Recycling waste trim is becoming more economically feasible due to the increasing value of the waste material, the increasing costs of solid waste disposal, and the decreasing availability of landfills. Many plastic articles are composite in nature. Articles, for example, automotive instrument panels may have a shell of harder denser plastic material, for example polyvinyl chloride (PVC), and a backing made from a less dense foam material such as urethane. After formation of the article, the article is trimmed or cut into its final shape. Excess trim results from each article. It has been proposed to recycle the excess trim and reclaim the component plastic materials.
Reclaiming plastic materials have difficulties not found for other types of materials. Plastic material is not magnetic, therefor, the use of magnetic fields often used in the reclamation of ferrous materials is useless. It has been proposed to recycle the material of the composite plastic by chopping the composite plastic into smaller fragments and sorting the fragments by the type of plastic. Liquid float tanks have been proposed where less dense foam particles float and dense vinyl particles sink. This method requires de-watering of the particles and subsequent drying which adds to the recycling costs. Furthermore many plastics have a density near that of water and thus the liquid float tanks do not adequately sort out these types of plastic materials.
Another process is disclosed in U.S. Pat. No. 5,042,725 issued to Robert A. Grimmer on Aug. 27, 1991. The Grimmer patent discloses a process for separating urethane foam and PVC particles from composite plastic parts by granulation of the composite parts to constituent foam and PVC particles. Larger particles are then separated from smaller particles by a screen. After the particles are sized, the foam and PVC particles are then separated by passing them through a separation table. The table uses air flow to levitate the less dense foam particles and allows the PVC particles to be at a lower level. The table is vibrated to direct the foam and PVC particles to different ducts.
The separation table described in the Grimmer patent has been utilized with flap doors at the duct for the discharge of the denser particles. The flap doors are aligned adjacent each other along the width of the duct and each is hinged at its top edge. Each flap door can independently swing to let the denser plastic material be discharged thereunder. However, some particles of less dense material are discharged between the openings created between the adjacent flap doors. Secondly, the flap doors may be prone to excess opening thereby allowing the less dense material to be discharged under the flap doors and contaminating the reclaimed PVC.
It has been found that the presence of only a small percentage of foam in the reclaimed PVC is enough to contaminate the reclaimed material such that it becomes unacceptable for known subsequent manufacturing processes. Furthermore only a small percentage of contamination is enough to render the reclaimed foam useless for further processing.
What is needed is an expediate reclamation process for composite urethane foam and PVC plastic parts that produces sufficiently pure reclaimed PVC and foam for subsequent known recycling processes.